Add license headers to source files

[rolker]

License headers missing from source files

package.xml declares the BSD license and the repo carries a LICENSE file, but the C++ sources under src/ and test/ have no copyright/license headers.

Adding headers to every source file (~130 files) is too invasive for the onboarding batch (PR #166), so it is deferred here per workspace ADR-0008.

Suggested approach when picked up:

• Add a standard BSD header block matching LICENSE to all .h/.cpp files
• Consider wiring ament_copyright (or a pre-commit hook) at the same time so the standard is enforced going forward

Part of #165 (onboarding). Identified by the onboard-project skill.

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Authored-By: Claude Code Agent
Model: Claude Fable 5